1. Field of the Invention
The present invention relates to a sample holder. In particular, the invention relates to a sample holder which has a means capable for tilting a sample around an axis with no relation to the existence of a fulcrum retaining member at the tilt axis.
2. Related Art Statement
FIG. 1 shows a diagrammatic illustration of a sample holder which has a means for tilting the sample with axes parallel (hereinafter called α tilt) and perpendicular (hereinafter called β tilt) to a long side of the holder body. Such a sample holder is typically used for electron microscopes such as a transmission electron microscope (TEM), a scanning transmission electron microscope (STEM) or the like.
There have been sample holders which comprise a holder body, a sample retaining stage and a sample retaining member. For example, a tilted sample stage has been invented since the tilt angle for the sample is notably restricted in the electron microscopes (JP-A 2001-15056, this is hereinafter called the patent reference 1).
However, in the prior art that essentially needs a fulcrum retaining member as shown in FIG. 1, there is the following problem: it is difficult to ensure a large α tilt angle because of interference between the fulcrum retaining member 15 for the β tilt stage 16 and upper 13 and lower 14 objective lens pole pieces (hereinafter called P-Ps) with a restricted spatial gap.
In other words, when the electron microscope observation is performed using a sample holder equipped with a double-tilt (α- and β-tilt) mechanism and a sample 17 supported at an apical portion of the sample holder is subsequently inserted and α-tilted at a cross-over point of the optical axis 10 and the focal plane 11 located between the upper 13 and lower 14 P-Ps, a large α tilt angle is not ensured since the fulcrum retaining member 15 interferes with the upper 13 and lower 14 P-Ps.
Further, in characteristic X-ray measurements, because the fulcrum retaining member 15 is a barrier to an emission pathway of characteristic X-rays, α tilt is needed in order to avoid the barrier. Namely, both the α- and β-tilt functions are required depending on the shape and crystallographic orientation of the sample in the characteristic X-ray measurements, and an X-ray detector is set between the upper P-P 13 and the focal plane 11 in order to detect X-rays emitted from the sample to the detector direction 12. As a result, the fulcrum retaining member for the β tilt 15 becomes a barrier to the emission pathway of the characteristic X-rays, and additional α tilt is needed for avoiding the barrier.
Furthermore, it is impossible to remove the sample stage 16 and exchange it with another sample stage, because the sample stage 16 capable for the β tilt is incorporated into the fulcrum retaining member 15. In the characteristic X-ray measurements, characteristic X-rays are generated from the sample stage as background since the electron beam in the electron microscope actually illuminates the sample stage as well as the sample. The influence of the background X-rays from the sample stage can be quantitatively measured by changing the material for the sample stage. However, it is actually necessary to prepare a number of sample holders with the sample stage 16 made of different materials, since the sample stage 16 has been incorporated into the member 15 for the β tilt.
The same problem described above exists in the patent reference 1. In the patent reference 1, there is a tilted sample stage to compensate the α tilt. However, a fulcrum retaining member such as the member 15 is still needed in order to add a β-tilt function. This means that nothing can hold and tilt the sample stage without the fulcrum retaining member; otherwise the stage is floating in the air.
In addition, there is another problem: although such a fulcrum retaining member as described above must be generally needed for ensuring mechanical strength of the holder itself, the member becomes a barrier to the movement of α tilt. Therefore, an art for attaining the β-tilt function without using a fulcrum retaining member is being desired. However, such a technique is unknown up to now.